From b95efe8dd3e663959b58d9139d32ca6c35884569 Mon Sep 17 00:00:00 2001
From: binwiederhier <phil@heckel.io>
Date: Mon, 23 Mar 2026 12:54:13 -0400
Subject: [PATCH] Tighten message IDs in attachments

---
 attachment/store.go | 14 +++++---------
 model/model.go      | 21 +++++++++++++--------
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/attachment/store.go b/attachment/store.go
index a9eaaeae..70fb55c0 100644
--- a/attachment/store.go
+++ b/attachment/store.go
@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"regexp"
 	"sync"
 	"time"
 
@@ -20,10 +19,7 @@ const (
 	orphanGracePeriod = time.Hour        // Don't delete orphaned objects younger than this to avoid races with in-flight uploads
 )
 
-var (
-	fileIDRegex      = regexp.MustCompile(fmt.Sprintf(`^[-_A-Za-z0-9]{%d}$`, model.MessageIDLength))
-	errInvalidFileID = errors.New("invalid file ID")
-)
+var errInvalidFileID = errors.New("invalid file ID")
 
 // Store manages attachment storage with shared logic for size tracking, limiting,
 // ID validation, and background sync to reconcile storage with the database.
@@ -86,7 +82,7 @@ func newStore(backend backend, totalSizeLimit int64, attachmentsWithSizes func()
 // from the client's Content-Length header; backends may use it to optimize uploads (e.g.
 // streaming directly to S3 without buffering).
 func (c *Store) Write(id string, reader io.Reader, untrustedLength int64, limiters ...util.Limiter) (int64, error) {
-	if !fileIDRegex.MatchString(id) {
+	if !model.ValidMessageID(id) {
 		return 0, errInvalidFileID
 	}
 	log.Tag(tagStore).Field("message_id", id).Debug("Writing attachment")
@@ -107,7 +103,7 @@ func (c *Store) Write(id string, reader io.Reader, untrustedLength int64, limite
 
 // Read retrieves an attachment file by ID
 func (c *Store) Read(id string) (io.ReadCloser, int64, error) {
-	if !fileIDRegex.MatchString(id) {
+	if !model.ValidMessageID(id) {
 		return nil, 0, errInvalidFileID
 	}
 	return c.backend.Get(id)
@@ -118,7 +114,7 @@ func (c *Store) Read(id string) (io.ReadCloser, int64, error) {
 // started and before the first sync) are corrected by the next sync() call.
 func (c *Store) Remove(ids ...string) error {
 	for _, id := range ids {
-		if !fileIDRegex.MatchString(id) {
+		if !model.ValidMessageID(id) {
 			return errInvalidFileID
 		}
 	}
@@ -166,7 +162,7 @@ func (c *Store) sync() error {
 	var count, totalSize int64
 	sizes := make(map[string]int64, len(remoteObjects))
 	for _, obj := range remoteObjects {
-		if !fileIDRegex.MatchString(obj.ID) {
+		if !model.ValidMessageID(obj.ID) {
 			continue
 		}
 		if _, ok := attachmentsWithSizes[obj.ID]; !ok && obj.LastModified.Before(cutoff) {
diff --git a/model/model.go b/model/model.go
index 97fecf2d..b3dae915 100644
--- a/model/model.go
+++ b/model/model.go
@@ -19,8 +19,8 @@ const (
 	PollRequestEvent   = "poll_request"
 )
 
-// MessageIDLength is the length of a randomly generated message ID
-const MessageIDLength = 12
+// messageIDLength is the length of a randomly generated message ID
+const messageIDLength = 12
 
 // Errors for message operations
 var (
@@ -133,10 +133,20 @@ func NewAction() *Action {
 	}
 }
 
+// GenerateMessageID creates a new random message ID
+func GenerateMessageID() string {
+	return util.RandomString(messageIDLength)
+}
+
+// ValidMessageID returns true if the given string is a valid message ID
+func ValidMessageID(s string) bool {
+	return util.ValidRandomString(s, messageIDLength)
+}
+
 // NewMessage creates a new message with the current timestamp
 func NewMessage(event, topic, msg string) *Message {
 	return &Message{
-		ID:      util.RandomString(MessageIDLength),
+		ID:      GenerateMessageID(),
 		Time:    time.Now().Unix(),
 		Event:   event,
 		Topic:   topic,
@@ -173,11 +183,6 @@ func NewPollRequestMessage(topic, pollID string) *Message {
 	return m
 }
 
-// ValidMessageID returns true if the given string is a valid message ID
-func ValidMessageID(s string) bool {
-	return util.ValidRandomString(s, MessageIDLength)
-}
-
 // SinceMarker represents a point in time or message ID from which to retrieve messages
 type SinceMarker struct {
 	time time.Time